A fertilized, incubated chicken egg takes about 21 days to hatch; and while most of us have seen what chicks look like at either end of the developmental spectrum (either sunny-side-up in a frying pan or newly hatched in a nature documentary), the fact that egg shells aren't see-through means that not many people have seen what goes on between days 2 and 20.

Well... now you have.

As reddit user alukima points out, it's unclear whether these photos catalogue the development of a single chick, or of several chicks photographed at different stages of development. You'll notice, for example, that in the third image the yolk appears be broken, but looks fine in later images.